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2007 Publications

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Microgrid Fault Protection Based on Symmetrical and Differential Current Components
The objective of this study was to develop a systematic approach for protecting a microgrid, in particular the AEP microgrid, against Single Line-to-Ground and Line-to-Line faults. A microgrid is a part of a large power system in which a number of sources, usually attached to a power electronic converter, and loads are clustered so that the microgrid can operate independent of the main power system. In general, a microgrid can operate in both the grid-connected mode and the islanded mode where the microgrid is disconnected from the main power system by a fast semiconductor switch called static switch. The report first describes the structure of the AEP microgrid and its protection zones are described. Then, the results obtained for the symmetrical current components related to unbalanced load conditions and SLG and LL faults in all protection zones are presented. Coordination of the protective relays of the AEP microgrid, based on the results obtained for symmetrical current components, are also discussed. The results of studies carried out on the AEP microgrid for SLG and LL faults in all protection zones of the microgrid are presented. Conclusions are stated in the last section of the report.

Prepared for Public Interest Energy Research California Energy Commission by Wisconsin Power Electronics Research Center, Department of Electrical and Computer Engineering, University of Wisconsin-Madison, December 2006.  
Hassan Nikkhajoei and Robert H. Lasseter 02/07/07 2.12 MB PDF 07-03
Where is the Edge for Cascading Failure?: Challenges and Opportunities for Quantifying Blackout Risk
Quantifying the overall risk of blackout due to cascading failure and determining the corresponding safe limits for power system design and operation are challenging problems. Large blackouts involve long, complicated and diverse cascades of events that often are unlikely or unexpected. An exhaustive and detailed analysis of these cascading events before the blackout occurs is impossible because of the huge number of possible combinations of unlikely events. Despite these challenges, approaches to quantify the overall risk of blackouts are emerging and we give a tutorial account reviewing these emerging approaches and their prospects. We summarize the implications for blackout risk of the power-law region in the observed distribution of sizes of North American blackouts. High-level probabilistic models of cascading failure and power system simulations suggest that there is a critical loading at which expected blackout size sharply increases and there is a power law in the distribution of blackout size. This critical loading could serve as a reference point for determining the "edge" for cascading failure risk. We model cascading failure as an initial disturbance that sometimes propagates to become much more widespread. The size of the initial disturbance and the average amount of propagation of the failures can be estimated from data from simulated cascades. We suggest that these estimates could be used to efficiently quantify the blackout risk. We summarize initial testing on power system simulations of cascading overloads and speculate that extending this approach to process data from series of cascades occurring in the power system could lead to direct monitoring of power system reliability.

This paper is for a panel session at the IEEE PES General Meeting in Tampa, FL, USA, June 2007. Uploaded: February 6, 2007.
2007 IEEE Power Engineering Society General Meeting, Panel Session, Tampa, Florida, June 2007.  
Ian Dobson 02/07/07 255.67 KB PDF 07-04
Stochastic Co-optimization for Hydro-Electric Power Generation
This paper proposes a stochastic programming framework for solving the optimal scheduling problem faced by a hydro-electric power producer that simultaneously participates in multiple markets. Specifically, the hydro-generator participates in both the electricity spot market and the ancillary services market as a price taker. It seeks to maximize its profit by jointly optimizing its energy/capacity sales and scheduling into all markets subject to market uncertainties and operational constraints. The impact of market uncertainties on the co-optimization problem over a pre-specified time horizon is analyzed through the stochastic programming formulation incorporating both ancillary service and market price uncertainties. Numerical case studies on the advantages of the proposed stochastic co-optimization strategy for a hydro-generator to hedge market uncertainties are carried out with a set of realistic parameters. The proposed model can also be adapted for determining the optimal scheduling and bidding strategy for a power producer facing additional types of market and operational uncertainties.

Presented at the INFORMS Annual Meeting, Pittsburg, PA, Nov. 2005. Uploaded: March 21, 2007.
2006 IEEE PES Power Systems Conference and Exposition, Atlanta, Georgia, October 29-November 1, 2006.  
Shi-Jie Deng, Youxun Shen, and Haibin Sun 03/21/07 425.25 KB PDF 07-05
Electricity Price Curve Modeling by Manifold Learning
This paper proposes a novel non-parametric approach for the analysis and prediction of electricity price curves by applying the manifold learning methodology. Cluster analysis based on the embedded low-dimensional manifold of the original price data is employed to identify characteristics of the price curve shape. The proposed price curve model performs well in forecasting both short-term price such as the day-ahead prices and longer term price such as the week-ahead prices. The forecast accuracy is demonstrated by numerical results using historical price data taken from the Eastern U.S. electric power markets.

Uploaded: March 21, 2007. EEE TRANSACTIONS ON POWER SYSTEMS, VOL. 23, NO. 3, AUGUST 2008.  
Jie Chen, Shi-Jie Deng, and Xiaoming Huo 07/06/17 1.01 MB PDF 07-06
Do Generation Firms in Restructured Electricity Markets Have Incentives to Support Socially-Efficient Transmission Investments?
This paper examines the incentives that generation firms have in restructured electricity markets for supporting long-term transmission investments. In particular, we study whether generation firms, which arguably play a dominant role in the restructured electricity markets, have the incentives to fund or support social-welfare-improving transmission investments. We examine this question and explore how such incentives are affected by the ownership of financial transmission rights (FTRs) by generation firms. We investigate the way in which the allocation of FTRs may be used to both align the incentives for supporting transmission expansions of the different market participants and mitigate conflicts of interest when such expansions are socially beneficial. Specifically, we show that if all FTRs were allocated or auctioned off to generation firms that are net exporters, then these firms would have the correct incentives to support social-welfare-improving transmission expansions. We illustrate these ideas in a simple two-node network.
Uploaded: April 13, 2007.  
Enzo E. Sauma and Shmuel S. Oren 09/19/07 370.14 KB PDF 07-07a
Do Generation Firms in Restructured Electricity Markets Have Incentives to Support Social-Welfare-Improving Transmission Investments?
Abstract—This paper examines the incentives that generation firms have in restructured electricity markets for supporting long-term transmission investments. In particular, we study whether generation firms, which arguably play a dominant role in the restructured electricity markets, have the incentives to fund or support incremental social-welfare-improving transmission investments. We examine this question in a two-node network and explore how such incentives are affected by the ownership of financial transmission rights (FTRs) by generation firms. In the analyzed two-node network, we show both (i) that a socially-concerned regulator should restrict the ownership of FTRs by the net importer generation firm because that may produce a disincentive to support incremental transmission expansions that increase both consumer surplus and social welfare and (ii) that the net exporter generation firm has the correct incentives to increase the transmission capacity incrementally up to a certain level. Moreover, if all FTRs were allocated or auctioned off to the net exporter generation firm, then it is possible to increase both consumer surplus and social welfare while keeping the net exporter generation firm revenue neutral.

(#07-27 re-named #07-07b.) Uploaded: September 18, 2007. Energy Economics, vol. 31, issue 5, pages 676-689, September 2009.  
Enzo E. Sauma, Shmuel S. Oren 07/08/16 607.51 KB PDF 07-07b
The Assessment of the Measurement of the Poynting Vector for Power System Instrumentation
The concept of using the Poynting vector to measure power system quantities is examined critically. The properties of this vector are described and a potential value in the area of in-strumentation of losses is discussed. The main difficulties are highlighted. Potential application areas lie in the instrumentation of high voltage insulator losses and transmission class reactor losses.

Submitted to the 2007 North American Symposium, Las Cruces, NM, October 2007. Uploaded: April 26, 2007.
NAPS 2007: The 39th North American Power Symposium, Las Cruces, New Mexico, September 30-October 2, 2007.  
Jonathan W. Stahlhut, Timothy J. Browne, Gerald T. Heydt 07/07/16 1.76 MB PDF 07-09
A Comparison of Local vs. Sensory, Input-Driven, Wide Area Reactive Power Control
In the evolution of wide area measurement systems (WAMS) to wide area control systems (WACS), several subsystems can be considered. One such subsystem to be considered under WACS is shunt capacitor switching strategies to provide reactive power support. Many shunt capacitors are operated using local voltage control, but WACS controlled shunt capacitors are operated remotely using a system wide strategy. A WACS control of capacitor switching is proposed based on indices that assess bus voltage magnitude and complex line flows. The switching scheme which produces operationally acceptable bus voltage magnitudes or line power flows, or a combination of the two phenomena, is used for global control of reactive power support. The differences between WACS and local control are illustrated utiliz-ing the IEEE 57 bus system as a test bed. A strategy based on the grouping of capacitors for WACS control is illustrated and com-pared to local control. Results show that WACS has better re-sults when the number of bus voltage magnitudes out of range and total system losses are considered as assessment measures of control effectiveness.

Proceedings of the 2007 IEEE Power Engineering Society General Meeting, Tampa, Florida, June 24-28, 2007. Uploaded: April 26, 2007.  
Project Leader: Gerald Heydt, Arizona State 07/08/16 199.56 KB PDF 07-10
Modeling of Suppliers' Learning Behaviors in a Market Environment
An important objective of electricity suppliers is to maximize their profits over a planning horizon and comply with the market rules. This objective requires suppliers to learn from their bidding experience and behave in an anticipatory way. With volatile Locational Marginal Prices (LMPs), ever-changing transmission grid conditions, and incomplete information about other market participants, decision making for a supplier is a complex task. A learning algorithm that does not require an analytical model of the complicated market but allows suppliers to learn from experience and act in an anticipatory way is a suitable approach to this problem. Q-Learning, an anticipatory reinforcement learning technique, has all these desired properties. Therefore, it is used in this research to model the learning behaviors of electricity suppliers in a Day-Ahead electricity market. The Day-Ahead electricity market is modeled as a multi-agent system with interacting agents including supplier agents, Load Serving Entities and a Market Operator. Simulation of the market clearing results under the scenario in which agents have learning capabilities is compared with the scenario where agents report true marginal costs. It is shown that, with Q-Learning, electricity suppliers are making more profits compared to the scenario without learning due to strategic gaming. As a result, the LMP at each bus is substantially higher.

Submitted to the 14th International Conference on Intelligent System Applications to Power Systems (ISAP 2007), Toki Messe, Niigata, Japan, November 5-8, 2007. Uploaded: April 27, 2007.  
Chen-Ching Liu, Leigh Tesfatsion 07/08/16 382.91 KB PDF 07-11
A Probabilistic Graphical Approach to Computing Electricity Price Duration Curves under Price and Quantity Competition
The electricity price duration curve (EPDC) represents the probability distribution function of the electricity price considered as a random variable. The price uncertainty comes both from the demand side and the supply side, since the load varies continuously, and not all generators may be available at all times. The production costs of electricity also fluctuate with the price of fuel. EPDCs have many application including the valuation of incremental generation assets or forward contracts on the energy produced by such assets, estimating capacity cost recovery and valuation of energy call options. Traditional approaches for calculating EPDCs were based on approximation methods such as the method of cumulants using Edgeworth expansions of multivariate probability distributions. This paper presents a new approach to compute numerically the EPDC under price and quantity competition models. This numerical method provide both exact numerical results and modeling flexibility. It is based on inference algorithms in probabilistic graphical models (PGMs) which exploit conditional independence relationships among the random variables.

Proceedings of the 39th Hawaii International Conference on System Sciences (HICSS 2007), Waikoloa, Hawaii, January 3-6, 2007. Uploaded: April 27, 2007.  
Shmuel Oren 07/08/16 469.06 KB PDF 07-12
A Next Generation Alarm Processing Algorithm Incorporating Recommendations and Decisions on Wide Area Control
The number of alarms for a typical power system event may be overwhelming to power system operators and may delay the operator from taking appropriate corrective action. Worldwide, a number of alarm processing techniques are used to reduce the number of alarms that the operator ‘sees’, so as to better comprehend the situation at hand and make accurate decisions faster. This paper proposes an alarm processing algorithm that goes beyond the prioritization of alarms. The conceptual algorithm proposed has additional features that offer the operator recommendations and decisions for the event that has caused the alarms, as well as a feature that may execute controls if the event is non critical. In this sense, the proposal is a bridge from wide area measurement to wide area control systems.

Proceedings of the IEEE 2007 PES General Meeting, Tampa, Florida, June 24-28, 2007. Uploaded: April 30, 2007.  
Elias Kyriakides, Jonathan Stahlhut, Gerald Heydt 04/30/07 121.98 KB PDF 07-13
Visualization and Characterization of Stability Swings via GPS-Synchronized Data
This paper provides a methodology to characterize the accuracy of PMU data (GPS synchronized) and the applicability of this data for monitoring system stability via visualization methods. GPS-synchronized equipment (PMUs) is in general higher precision equipment as compared to typical SCADA systems. Conceptually, PMU data are time tagged with precision better than 1 microsecond and magnitude accuracy that is better than 0.1%. This potential performance is not achieved in an actual field installation due to errors from instrumentation channels and system imbalances. Presently, PMU data precision from substation installed devices is practically unknown. On the other hand, specific applications of PMU data require specific accuracy of data. Applications vary from simple system monitoring to wide area protection and control to voltage instability prediction and transient stability monitoring. The paper focuses on the last application, i.e. transient stability monitoring. We propose an approach that is based on accurate evaluation of the system energy function (Lyapunov indirect method) and extraction of stability properties from the energy function. Specifically, we provide a methodology for determining the required data accuracy for the reliable real time estimation of the energy function. When the data meet these requirements, the estimated energy function can be visualized and animated providing a powerful visual tool for observing the transient stability or instability of the system.

Proceedings of the 40th Annual Hawaii International Conference on System Sciences (HICSS 2007), Waikoloa, Hawaii, January 3-6, 2007. Uploaded: April 30, 2007.  
George J. Cokkinides, A. P. Sakis Meliopoulos, George Stefopoulos, Ramiz Alaileh and Apurva Mohan 04/30/07 236.04 KB PDF 07-14
Border Flow Rights and Contracts for Differences of Differences: Models for Electric Transmission Property Rights
In this paper a property rights model for electric transmission is proposed and its properties analyzed. The proposed rights, called “border flow rights,” support financial hedging of transmission risk and merchant transmission expansion through associated financial rights, called “contracts for differences of differences.” These financial rights allow for forward trading of both energy and transmission by a unified exchange, avoiding the bifurcation in current markets between decentralized longterm energy trading and centralized long-term transmission trading. Such long-term trading can help to support the financing of both generation and transmission assets. We consider incentive properties of such a right in the absence of lumpiness, economies of scale, and market power.

Uploaded May 3, 2007. IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 22, NO. 4, NOVEMBER 2007.  
Ross Baldick 07/08/16 203.65 KB PDF 07-15
Challenges of Integrating Large Amounts of Wind Power
Wind energy has experienced remarkable growth over the last decade, due in part to renewed public support and maturing turbine technologies. But often hidden from public view are the difficulties and challenges associated with introducing a new technology into an older electrical system of established infrastructure. Many early wind turbines utilized a squirrel-cage or wound-rotor induction generator to produce electricity. These generators allowed small variations in rotor speed thus improving energy capture and reducing torque shocks caused by wind gusts. However, they absorbed large amounts of reactive power and sometimes caused severe voltage stability problems on the grid. This paper explores some of the solutions that have resulted over the years, including the introduction of two new variable-speed generator types, doublyfed induction and synchronous machines. It also considers the evolution of new grid codes and turbine improvements that make wind energy more grid-compatible to ensure further growth of this promising renewable source of energy.

1st Annual IEEE Systems Conference Waikiki Beach, Honolulu, Hawaii, April 9-12, 2007. Uploaded: May 31, 2007.  
Jonathan Rose and Ian Hiskens 05/31/07 99.48 KB PDF 07-18
Towards More Flexible and Robust Data Delivery for Monitoring and Control of the Electric Power Grid
With the increase in the monitoring of status data at very high rates in high voltage substations and the ability to time synchronize these data with GPS signals, there is a growing need for transmitting this data for monitoring, operation, protection and control needs. The sets of data that need to be transferred and the speed at which they need to be transferred depend on the application – for example, slow for post-event analysis, near real-time for monitoring and as close to real-time as possible for control or protection. In this paper, we overview the requirements for the next-generation power grid’s communication infrastructure in the areas of flexibility and quality of service, with extensive citations of power industry practitioners and researchers, and analyze implementation options. We also overview technologies in the computer science field of distributed computing that can be brought to bear to help meet these requirements, yet to date have not been discussed in the context of grid modernization. Additionally, we argue against the industry trend of using either TCP/IP or web services for real-time data exchange for fast controls. We then describe GridStat, a novel middleware framework we have developed that is suitable for the power grid and its application programs. Test results demonstrate that such a flexible framework can also guarantee latency that is suitable for fast wide-area protection and control.

Technical Report EECS-GS-009, School of Electrical Engineering and Computer Science, Washington State University, Pullman, WA, May 30, 2007. Uploaded: June 5, 2007.  
David E. Bakken, Carl H. Hauser, Harald Gjermundrod, Anjan Bose 07/08/16 614.72 KB PDF 07-19
Microgrids and Distributed Generation
Application of individual distributed generators can cause as many problems as it may solve. A better way to realize the emerging potential of distributed generation is to take a system approach which views generation and associated loads as a subsystem or a “microgrid”. The sources can operate in parallel to the grid or can operate in island, providing UPS services. The system will disconnect from the utility during large events (i.e. faults, voltage collapses), but may also intentionally disconnect when the quality of power from the grid falls below certain standards. Utilization of waste heat from the sources will increase total efficiency, making the project more financially attractive. University of Wisconsin Laboratory verification of microgrid control concepts are included.

To appear in the Journal of Energy Engineering, American Society of Civil Engineers, vol. 133, no. 3, SPECIAL ISSUE: Distributed Energy Resources - Potentials for the Electric Power Industry, September 2007. Uploaded: June 5, 2007.  
Robert H. Lasseter 06/05/07 84.90 KB PDF 07-20
Microgrid Protection
In general, a microgrid can operate in both the grid-connected mode and the islanded mode where the microgrid is interfaced to the main power system by a fast semiconductor switch called static switch, (SS). It is essential to protect a microgrid in both the grid-connected and the islanded modes of operation against all types of faults. The major issue arises in island operation with inverter-based sources. Inverter fault currents are limited by the ratings of the silicon devices to around 2 p.u. rated current. Fault currents in islanded inverter based microgrids may not have adequate magnitudes to use traditional over-current protection techniques. The philosophy for protection is to have the same protection strategies for both islanded and grid-connected operation. The static switch is designed to open for all faults.

2007 IEEE PES General Meeting, Panel: Microgrid Research and Field Testing, Tampa, Florida, June 24-28, 2007. Uploaded: June 5, 2007.  
H. Nikkhajoei and Robert H. Lasseter 06/05/07 307.40 KB PDF 07-21
CERTS Microgrid
Application of individual distributed generators can cause as many problems as it may solve. A better way to realize the emerging potential of distributed generation is to take a system approach which views generation and associated loads as a subsystem or a “microgrid”. The sources can operate in parallel to the grid or can operate in island, providing UPS services. The system will disconnect from the utility during large events (i.e. faults, voltage collapses), but may also intentionally disconnect when the quality of power from the grid falls below certain standards. Utilization of waste heat from the sources will increase total efficiency, making the project more financially attractive. Field verification of the Consortium for Electric Reliability Technology Solutions (CERTS) microgrid control concepts are included.

2007 IEEE International Conference on System of Systems Engineering, Panel: Microgrid Systems, San Antonio, Texas, April 16-18, 2007. Uploaded: June 5, 2007.  
Robert H. Lasseter 06/05/07 212.93 KB PDF 07-22
Extended Microgrid Using (DER) Distributed Energy Resources
DER can provide for a more robust transmission system and enhance local reliability. This can be achieved by moving load following requirements to the distribution system and design for intentional islanding within the distribution system. The research results show that it is possible to control a distributed generator coupled with storage to maintain grid flow constant at all times. Furthermore, it is possible to achieve a steady state operation with a periodic loading profile while enforcing active power limits and energy storage limits. An energy reserve for the storage is necessary to guarantee power to the loads during an islanding event. The control of the clustered pair, generator plus storage, is identical to microgrid source control, with some added constraints on the active powers. These constraints depend on the configuration that one chooses to adopt, either generator or storage performing the base loading function while the other performs the peak shaving function.

2007 IEEE PES General Meeting, Tampa, Florida, June 24-28, 2007. Uploaded: June 5, 2007.  
Robert H. Lasseter and Paolo Piagi 06/05/07 69.70 KB PDF 07-23
Towards Quantifying Cascading Blackout Risk
Blackouts become widespread by initial failures propagating in a diverse and intricate cascade of rare events. We describe this complicated cascade using a bulk probabilistic model in which the initial failures propagate randomly according to a branching process. The branching process parameters can be statistically estimated from observed data or simulations and then used to efficiently predict the probability distribution of blackout size. We review the current testing of these methods on simulations and observed data and discuss the next steps towards achieving verified and practical methods for quantifying cascading failure of electric power systems. The ability to efficiently quantify cascading blackout risk from observed data and simulations could offer new ways to monitor power transmission system reliability and quantify the reliability benefit of proposed improvements.

2007 IREP Symposium - Bulk Power System Dynamics and Control - VII, Revitalizing Operational Reliability, Charleston, South Carolina, August 19-24, 2007. Uploaded: June 22, 2007.  
Ian Dobson, Kevin Wierzbicki, Janghoon Kim, Hui Ren 07/08/16 280.34 KB PDF 07-24
Complex Systems Analysis of Series of Blackouts: Cascading Failure, Critical Points, and Self-organization (CHAOS Journal)
We give an overview of a complex systems approach to large blackouts of electric power transmission systems caused by cascading failure. Instead of looking at the details of particular blackouts, we study the statistics and dynamics of series of blackouts with approximate global models. Blackout data from several countries suggests that the frequency of large blackouts is governed by a power law. The power law makes the risk of large blackouts consequential and is consistent with the power system being a complex system designed and operated near a critical point. Power system overall loading or stress relative to operating limits is a key factor affecting the risk of cascading failure. Power system blackout models and abstract models of cascading failure show critical points with power law behavior as load is increased. To explain why the power system is operated near these critical points and inspired by concepts from self-organized criticality, we suggest that power system operating margins evolve slowly to near a critical point and confirm this idea using a power system model. The slow evolution of the power system is driven by a steady increase in electric loading, economic pressures to maximize the use of the grid, and the engineering responses to blackouts that upgrade the system. Mitigation of blackout risk should account for dynamical effects in complex self-organized critical systems. For example, some methods of suppressing small blackouts could ultimately increase the risk of large blackouts.

CHAOS - An Interdisciplinary Journal of Nonlinear Science, vol. 17, no. 2, June 2007. Uploaded: July 12, 2007.  
Ian Dobson, Ben Carreras, Vickie Lynch, David Newman 07/08/16 617.88 KB PDF 07-25a
Complex Systems Analysis of Series of Blackouts: Cascading Failure, Critical Points, and Self-organization (2004 IREP Symposium)
We give an overview of a complex systems approach to large blackouts of electric power transmission systems caused by cascading failure. Instead of looking at the details of particular blackouts, we study the statistics and dynamics of series of blackouts with approximate global models. Blackout data from several countries suggests that the frequency of large blackouts is governed by a power law. The power law makes the risk of large blackouts consequential and is consistent with the power system being a complex system designed and operated near a critical point. Power system overall loading or stress relative to operating limits is a key factor affecting the risk of cascading failure. Power system blackout models and abstract models of cascading failure show critical points with power law behavior as load is increased. To explain why the power system is operated near these critical points and inspired by concepts from self-organized criticality, we suggest that power system operating margins evolve slowly to near a critical point and confirm this idea using a power system model. The slow evolution of the power system is driven by a steady increase in electric loading, economic pressures to maximize the use of the grid, and the engineering responses to blackouts that upgrade the system. Mitigation of blackout risk should account for dynamical effects in complex self-organized critical systems. For example, some methods of suppressing small blackouts could ultimately increase the risk of large blackouts.

2004 IREP Symposium - Bulk Power System Dynamics and Control - VI, Cortina d’Ampezzo, Italy, August 22-27, 2004. Uploaded: July 8, 2016.  
Ian Dobson, Ben Carreras, Vickie Lynch, David Newman 07/08/16 472.03 KB PDF 07-25b
Complex Systems Analysis of Series of Blackouts: Cascading Failure, Critical Points, and Self-organization (2004 IREP Symposium Leaflet)
Leaflet for the 2004 IREP Symposium - Bulk Power System Dynamics and Control - VI, Cortina d’Ampezzo, Italy, August 22-27, 2004.  
07/08/16 464.65 KB PDF 07-25c
Transmission Unit Commitment for Optimal Dispatch - Sensitivity Analysis and Extensions (CERTS Report)
Abstract—In this paper, we continue to analyze optimal dispatch of generation and transmission topology to meet load as a mixed integer program (MIP) with binary variables representing the state of the transmission line. Previous research showed a 25% savings by dispatching the IEEE 118 Bus system. This paper is an extension of that work. It presents how changing the topology impacts nodal prices, load payment, generation revenues, cost, and rents, congestion rents, and flowgate prices. Results indicate that choosing the optimal topology typically results in lower load paymetns and higher generation rents for this network. Computational issues are also discussed.

Consortium for Electric Reliability Technology Solutions (CERTS), Transmission Unit Commitment in Economic Dispatch, September 13, 2007. Uploaded: September 18, 2007.  
Kory W. Hedman, Richard P. O'Neill, Emily Bartholomew Fisher, Shmuel S. Oren 09/18/07 196.36 KB PDF 07-26a
Optimal Transmission Switching - Sensitivity Analysis and Extensions (IEEE Report)
Abstract - In this paper, we continue to analyze optimal dispatch of generation and transmission topology to meet load as a mixed integer program (MIP) with binary variables representing the state of the transmission line. Previous research showed a 25% savings by dispatching the IEEE 118 Bus system. This paper is an extension of that work. It presents how changing the topology impacts nodal prices, load payment, generation revenues, cost, and rents, congestion rents, and flowgate prices. Results indicate that choosing the optimal topology typically results in lower load paymetns and higher generation rents for this network. Computational issues are also discussed.

IEEE Transactions on Power Systems, vol. 23, issue 3, August 2008.  
Kory W. Hedman, Richard P. O'Neill, Emily Bartholomew Fisher, Shmuel S. Oren 07/08/16 704.94 KB PDF 07-26b
Optimal Static Hedging of Volumetric Risk in a Competitive Wholesale Electricity Market
Abstract—In competitive wholesale electricity markets, regulated load serving entities (LSEs) and marketers with default service contracts have obligations to serve fluctuating load at predetermined fixed prices while meeting their obligation through combinations of long-term contracts, wholesale purchases and self-generation that are subject to volatile prices or opportunity cost. Hence, their net profits are exposed to joint price and quantity risk both of which are correlated with weather variations. In this paper we develop a static hedging strategy for the LSE (or marketer) whose objective is to minimize a mean-variance utility function over net profit, subject to a self-financing constraint. Since quantity risk is non-traded, the hedge consists of a portfolio of price-based financial energy instruments, including a bond, forward contract and a spectrum of European call and put options with various strike prices. The optimal hedging strategy is jointly optimized with respect to contracting time and the portfolio mix, which varies with contract timing, under specific price and quantity dynamics and the assumption that the hedging portfolio which matures at the time of physical energy delivery is purchased at a single point in time. Explicit analytical results are derived for the special case where price and quantity have a joint bivariate lognormal distribution.

Uploaded: September 18, 2007. Decision Analysis, vol 7, no. 1, pp. 107-122, March 2010.  
Yumi Oum, Shmuel Oren 07/08/16 222.36 KB PDF 07-28
An Equilibrium Pricing Model for Weather Derivatives in a Multi-commodity Setting
Many industries are exposed to weather risk. Weather derivatives can play a key role in hedging and diversifying such risk because the uncertainty in a company's profit function can be correlated to weather condition which affects diverse industry sectors differently. Unfortunately the weather derivatives market is a classical example of an incomplete market that is not amenable to standard methodologies used for derivative pricing in complete markets. In this paper, we develop an equilibrium pricing model for weather derivatives in a multi-commodity setting. The model is constructed in the context of a stylized economy where agents optimize their hedging portfolios which include weather derivatives that are issued in a fixed quantity by a financial underwriter. The supply and demand resulting from hedging activities and the supply by the underwriter are combined in an equilibrium pricing model under the assumption that all agents maximize some risk averse utility function. We analyze the gains due to the inclusion of weather derivatives in hedging portfolios and examine the components of that gain attributable to hedging and to risk sharing.

Uploaded: September 18, 2007. Energy Economics, vol 31, no. 5, pp. 702-713, August 2009.  
Yongheon Lee, Shmuel S. Oren 07/08/16 562.43 KB PDF 07-29
Economic Consequences of Alternative Solution Methods for Centralized Unit Commitment in Day-Ahead Electricity Markets
Abstract—Many wholesale electricity markets call on the independent system operator (ISO) to determine day-ahead schedules for generators based on a centralized unit commitment. Up until recently, the Lagrangian relaxation (LR) algorithm was the only practical means of solving an ISO-scale unit commitment problems, and was the solution technique used by most ISOs. Johnson et al [1] demonstrate, however, that equity, incentive and efficiency issues will arise from use of LR solutions, because different commitments that are similar in terms of total system costs can result in different surpluses to individual units. Recent advances in computing capabilities and optimization algorithms now make solution of the mixed-integer programming (MIP) formulation by means of branch and bound (B&B) tractable, often with optimality gaps smaller than those of LR algorithms, which has led some ISOs to adopt B&B algorithms and others proposing to do so. With the move towards B&B, one obvious question is whether the use of MIP will eliminate or reduce the issues with LR raised by Johnson et al. Using actual market data from an ISO we demonstrate that both LR and MIP solutions will suffer the same equity issues, unless the ISO unit commitment problems can be solved to complete optimality within the allotted timeframe--which is beyond current computational capabilities. Our result further demonstrate that the size of the payoff deviations are not monotone in the size of the optimality gap, meaning smaller optimality gaps from B&B will not necessarily mitigate the issues Johnson et al raise. We show that the use of 'make-whole' payments, which ensure units recover any startup and no-load costs not recovered by inframarginal energy rents, can help to reduce surplus volatility and differences to some extent.

Uploaded: September 21, 2007. IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 23, NO. 2, MAY 2008.  
Ramteen Sioshansi, Richard O'Neill, Shmuel S. Oren 07/08/16 569.06 KB PDF 07-30
Transformer Thermal Modeling Improving Reliability Using Data Quality Control
Abstract—Eventually all large transformers will be dynamically loaded using models updated regularly from field measured data. Models obtained from measured data give more accurate results than models based on transformer heat-run tests and can be easily generated using data already routinely monitored. The only significant challenge to using these models is to assess their reliability and improve their reliability as much as possible. In this work, we use data quality control and data-set screening to show that model reliability can be increased by about 50% while decreasing model prediction error. These results are obtained for a linear model. We expect similar results for the nonlinear models currently being explored.

Uploaded: October 1, 2007. IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 21, NO. 3, JULY 2006.  
Daniel J. Tylavski, Xiaolin Mao, Gary A. McCulla 07/08/16 1.63 MB PDF 07-32
Assessing the Reliability of Linear Dynamic Transformer Thermal Modeling
Abstract—Improving the utilisation of transformers requires that the hot-spot and top-oil temperatures be predicted accurately. Using measured (noisy) data to derive equivalent linear dynamic thermal models yields performance that is superior to the ANSI standard model, but the reliability of these model coefficients must be assessed if the user is to have confidence in the model. By adding arbitrarily large amounts of data in the modelling process it was expected to make the reliability measures of these models arbitrarily small. When this did not happen, an investigation began that showed why there is a limitation to the accuracy of models derived from noisy data. It is also shown that a standard technique for assessing the reliability of model coefficients is invalid because of the absence of unmeasured driving variables. An alternative method for assessing transformer model reliability is provided.

Uploaded: October 1, 2007. IEE Proceedings - Generation, Transmission and Distribution, vol. 153, issue 4, July 13, 2006.  
Xiaolin Mao, Daniel J. Tylavsky, Gary A. McCulla 10/01/07 212.72 KB PDF 07-33
Acceptability of Four Transformer Top-Oil Thermal Models Part 1: Defining Metrics
Abstract—Eventually, prediction of transformer thermal performance for dynamic loading will be made using models distilled from measure data, rather than models derived from transformer heat-run tests. Which model(s) will be used for this purpose remains unclear. In this paper, we introudce metrics for measuring the acceptability of transformer thermal models. For a model to be acceptable, it must have the qualities of: adequacy, accuracy and consistency. We assess model adequacy using the metrics: prediction R2, and plot of residuals against fitted values. To assess model consistency, we use: variance inflation factor (VIP) (which measure multicollinearity), condition number, eigenstructure, parameter sensitivity and standard deviation (STD) of model parameters and of predicted maximum steady state load (SSL-max). To assess model accuracy we use comparison of model parameters with nominal values and error duration curves. Other metrics of interest are also introduced. In a companion paper, these metric are applied to the four models defined in this paper and a relative ranking of the acceptability of these models is presented.

Uploaded: September 28, 2007. IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 23, NO. 2, APRIL 2008.  
Lida Jauregui Rivera, Daniel J. Tylavsky 07/08/16 239.90 KB PDF 07-34
Acceptability of Four Transformer Top-Oil Thermal Models Part 2: Comparing Metrics
Abstract—The acceptability of four transformer top-oil thermal models are examined vis-à-vis training with measured data. Acceptability is defined as having the qualities of adequacy, consistency, and accuracy. Metrics are used to characterize the likely deficiencies of these models. It is shown that: the classical IEEE/ANSI standard model is unacceptable for model identification purposes. The linear top oil model is acceptable for FOFA transformers but not NOFA. The models by Susa et al. [7] and Swift et al. [5], [6], may be useful for FOFA transformers and NOFA transformers. Further research with larger training data sets is warranted.

Uploaded: September 28, 2007. IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 23, NO. 2, APRIL 2008.  
Lida Jauregui Rivera, Daniel J. Tylavsky 07/08/16 1.46 MB PDF 07-35
Interactive Lessons for Pre-University Power Education
A key need facing the electric power industry is the ongoing requirement to develop its future workforce. While university education is a crucial step in this process, studies have shown that many promising students are unaware of possible careers in the power industry. Many also lose interest in math and science during their high school and even middle school years. This paper presents lesson plans and associated applets designed to help address these needs, developed as a collaboration between electric power researchers and education specialists. Thus far, two units have been developed to engage pre-university students in the power area.
The first unit, Power and Energy in the Home, serves as an introduction to the concepts of power and energy and provides many sample loads to illustrate the impacts of running different appliances. Special attention is paid to environmental issues by the inclusion of Energy Star appliances along with incandescent and compact fluorescent lighting.
The second unit, titled The Power Grid, aims to inform students about the macroscopic picture of how energy gets from generators to loads. Many different generation technologies are included, along with external system connections to demonstrate how power is imported and exported. Discussion of line overloading, and how networks can be both beneficial and detrimental depending on circumstances, are facilitated by features built into the applet and provided in the lesson plans. The materials have been distributed to students and educators, many of whom have provided valuable feedback.

Uploaded: November 16, 2007. IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 23, NO. 3, AUGUST 2008.  
Zeb Tate, Tom Overbye, Jana Sebestik, George Reese 07/08/16 869.49 KB PDF 07-36
Line Outage Detection Using Phasor Angle Measurements
Although phasor measurement units (PMUs) have become increasingly widespread throughout power networks, the buses monitored by PMUs still constitute a very small percentage of the total number of system buses. Our research explores methods to derive useful information from PMU data in spite of this limited coverage. In particular, we have developed an algorithm which uses known system topology information, together with PMU phasor angle measurements, to detect system line outages. In addition to determining the outaged line, the algorithm also provides an estimate of the pre-outage flow on the outaged line. To demonstrate the effectiveness of our approach, the algorithm is demonstrated using simulated and real PMU data from two systems—a 37-bus study case and the TVA control area.

Submitted to IEEE Transactions on Power Systems, November 2007. Uploaded: November 16, 2007.
IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 23, NO. 4, NOVEMBER 2008.  
Zeb Tate, Tom Overbye 07/08/16 541.24 KB PDF 07-37
Transmission-Constrained Residual Demand Derivative in Electricity Markets
Abstract—The residual demand derivative plays a central role in constructing the best response to competitors’ strategies in widely used strategic models such as the Cournot model and the supply function model. In the absence of transportation or transmission constraints, the residual demand derivative is obtained straightforwardly by taking the derivative of the residual demand function with respect to price. However, in an electricity market, the market is embedded in a transmission network. When there is no transmission congestion, the residual demand derivative can be calculated as usual, but when there is transmission congestion, the residual demand derivative is more difficult to calculate. In this paper, we characterize the transmission-constrained residual demand derivative. We use the dc power flow model and characterize the residual demand derivative analytically.

Reprinted with IEEE permission from Lin Xu, Student Member, IEEE; and Ross Baldick, Fellow, IEEE; Transmission-Constrained Residual Demand Derivative in Electricity Markets. IEEE Transactions on Power Systems, vol. 22, no. 4, November 2007. Uploaded: January 13, 2009.

IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 22, NO. 4, NOVEMBER 2007.  
Ross Baldick and Lin Xu 01/13/09 219.83 KB PDF 07-39